Question 1: "Folate trapping" in a vitamin B12

Correct!

The suggested mnemonic to remember this is that, in the intersection between the folate and B12 pathways, it is methyl-folate that donates the methyl group to B12 to make methyl-B12. Of course, if there is no B12 around, this cannot happen, and the folate becomes trapped. The next question asks a bit more about methyl-B12...